A U.S. spy plane and a Chinese fighter jet collided over the South China Sea Sunday, increasing tensions at a time when U.S. officials are considering weapons sales to Taiwan.

China said the fighter jet crashed and its pilot was missing. The U.S. Navy EP-3 surveillance plane made an emergency landing on Hainan island in southern China. The 24 American crew members weren't injured, said a spokesman for the U.S. Pacific Command in...